A polarization-aware physics-based rendering (PBR) engine uses a Mueller matrix (MM)-valued polarized bidirectional reflectance distribution function (pBRDF) as a characterization of a given material's polarized light scattering behavior. To evaluate the ability of the pBRDF to predict polarized light scattering, this work creates a validation loop between pBRDF characterization, scene renderings, and MM imaging of scenes. A conventional method for pBRDF sampling is MM imaging of spherical objects so that many scattering geometries are simultaneously captured. This pBRDF serves as input to a polarization-aware PBR engine for rendering arbitrary object shapes and illumination geometries. In this work, spheres and the components of a Cornell box are 3D-printed to create a set of shapes made of the same material. Then a validation loop is created where the pBRDF from sphere MM measurements are used for polarimetric renderings which are compared to MM images of the Cornell box. The generalization of the pBRDF is tested using different shapes for measurement or polarimetric rendering. For example, multiple surface interactions inside the Cornell box will create polarimetric effects that are not observed by measuring spheres. The pBRDF's ability to generalize varying lighting geometries and adjacency effects will be tested.

Multiple scattering of light in biological tissues rapidly scrambles polarization, so polarimetric biomedicine is challenging. Nevertheless, there are ways to mitigate these and other tissue-specific challenges to extract useful biophysics via both Stokes and Mueller matrix analyses. In this talk, I will highlight our ongoing studies of tissue birefringence in histology-like thin-sample transmission geometry (potential applications for breast and colorectal cancer), and in thick-tissue reflection geometry (potential applications for intraoperative surgical guidance). Enabling technology approaches, preclinical results, and selected patient studies will be highlighted

In turbid tissue-like scattering medium the conventional polarised light, scattered multiple number of times, is depolarised, and the depolarisation rate depends strongly on the size and shape of scattering particles, as well as on the number of scattering events. In fact, the structure of light can be more complicated when the polarisation of light across the laser beam can be radially or azimuthally polarised and carry orbital angular momentum (OAM). We use both conventional polarisation and shaped light with OAM for characterisation of biological tissues and their structural malformations associated with dangerous diseases, including cancer, dementia, diabetes and other.

An ideal unpolarized light should have random instantaneous polarization states covering the entire Poincare sphere with equal probability. Light beams, which are otherwise known as unpolarized, do not always satisfy this criterion. Wolf’s definition of the degree of polarization cannot account for these differences. Hence, we define the degree of genuine unpolarization (DoGUP)—a metric that assigns a maximum value to the ideal unpolarization and dictates how far an unpolarized field is from the ideal case. To define the DoGUP, we introduce the polarization probability space (PPS) concept and illustrate using a two-mode Fock state.

The polarization sensitivity of a nano-optical array is hypothesized to correlate with the degree of asymmetry of its individual nanostructures. This work takes a top-down approach to investigate how controlled violations of two-dimensional symmetry in regular polygon-shaped nanostructures affect the polarization sensitivity of lattice resonant, dielectric nano-arrays. Such nanoarrays dampen higher-order Mie resonances while maintaining the fundamental Mie resonance. Isolating a fundamental Mie resonance in the visible region of the electromagnetic spectrum permits the mapping of a spectrum to a high-purity color. Through this, it becomes possible to build a colorimetric sensor of domains of rotations of linearly polarized light.

This conference presentation was prepared for SPIE Optics + Photonics, 2023.

Recently our team published results on the reconstruction of photoelastic modulator (PEM)-based Mueller polarimeters applying the complete Q-matrix to a 9-element partial Mueller polarimeter with temporal modulation comprised by two PEM-polarizer pairs. In this investigation we extended the application of the Q-matrix to a complete 4-PEM Mueller polarimeter comparing the results with the analytical solution in the frequency domain and the complete temporal basis method. It is expected that the frequency-based analysis will allow to study signals with a broader bandwidth and the linear algebra-based methods will account for more information, otherwise ignored by the analytical solution.

A portable Mueller matrix imaging spectropolarimeter is presented, optimized for high throughput optical plant phenotyping, by combining a temporal and spatial modulation scheme. Critical aspects of the design included minimizing the measurement time while maximizing signal-to-noise ratio by mitigating systematic error for wavelengths spanning 405-730 nm. Validation results, which were taken in a redundant and non-redundant measurement configuration, indicated that the polarimeter provides an average absolute error of 5.3E-3 +/- 2.2E-3 and 7.2E-3 +/- 3.1E-3, respectively. Baseline polarization measurements are also provided of normal and barren Zea Maize hybrids (G90).

We propose a RGB full- Stokes video imager by two RGB microgrid polarization cameras with linear micro-polarizer array which is aligned to 0, 45, 90 and 135° of azimuthal direction. It is mainly applied to calibrate retarder and non-polarizing beam splitter with wavelength dependence. A presentation highlights applying for a bio-polarization imager to demonstrate a bio-imaging using a differential interferometric microscope, microplastics and polarization properties of incents .

Metasurfaces are diffractive optical elements composed of subwavelength structures that, when leveraging birefringence, can serve as multifunctional freespace polarization optics. Metasurface gratings are flat optical elements designed to operate as full Stokes analyzers to enable compact polarimetric imaging. This work presents the calibration of a metagrating-based Stokes imaging system. A prototype metasurface full Stokes imaging polarimeter concept is compared to a benchtop instrument for 670, 532, and 460 nm metagratings. The metagrating Stokes imaging polarimeters are assessed for DOLP accuracy within ±0.5%. The 532 nm instrument is fully evaluated for polarization ellipse and degree of polarization accuracy.

Many particles in nature, such as ice crystals in cirrus clouds and airborne dust aerosol particles, are nonspherical with complex geometries. The scattering of polarized light by nonspherical particles is inevitably necessary for numerous disciplines, including polarimetric remote sensing. In this presentation, we report an advanced light-scattering computational capability, referred to as the synergistic light-scattering computational method, which is based on a combination of the invariant imbedding T-matrix method and the physical-geometric optics method. The former is applied to small to moderately large particles, whereas the latter is applicable to moderate to large particles. In particular, we illustrate the smooth transition of the results obtained with the two methods. Furthermore, we demonstrate the applications of the advanced light-scattering computational capability in polarimetric remote sensing.

We have developed and deployed a mast-mounted hyperspectral imaging polarimeter (HIP) and imaged corn fields across multiple diurnal cycles and growing seasons. Using the polarization data, we present results and methods demonstrating the use of polarized bidirectional reflectance distribution functions (pBRDFs) to correct for surface glare when measuring light more deeply scattered from the tissues. This technique reduces time of day, solar incidence angle, and viewing angle as confounding factors for spectral measurements.

To facilitate polarimetric remote sensing of the earth system, we develop a vector radiative transfer model, namely, Texas A&M University vector radiative transfer model (TAMU-VRTM), to simulate the propagation of polarized light in the atmosphere-ocean-land system (AOLS). The model includes a Jacobian computational model, which can efficiently compute the analytical first derivatives of the observables to all the model input. The TAMU-VRTM can be seamlessly incorporated into an inversion algorithm to retrieve the atmospheric, oceanic and land properties from the spaceborne radiometric and polarimetric observations. This presentation will illustrate the application of the model in spaceborne polarimetric remote sensing.

Quantitative information about invasion depth of cancer in early stages is very beneficial to cancer diagnosis, which is difficult to obtain accurately using current biological imaging technologies. Circularly polarized light scattering method proposed as a novel biomedical evaluation technique can provide depth profile by varying the incident or detection angles of CPL as well as wavelength of CPL. This paper reports the results of Monte Carlo simulations and experiments to demonstrate cancer depth estimation using this technique.